The present invention relates to an apparatus for controlling the idling operation of an internal combustion engine, more particularly to an idling operation controlling apparatus for a multi-cylinder internal combustion engine for regulating the fuel supplied for each cylinder so as to minimize the dispersion in output among the respective cylinders thereby enabling stable control of the idling operation with good response characteristics.
In the conventional control system for controlling the amount of fuel injected from a fuel injection pump into a multi-cylinder internal combustion engine, the fuel injection amounts for the respective cylinders are uniformly controlled in common. Accordingly, uniform output cannot be obtained from the cylinders due to dimensional differences etc. within the manufacturing tolerance of the internal combustion engine and/or the fuel injection pump and the like. Non-uniform output of the cylinders causes especially pronounced degradation in the stability of the internal combustion engine during the idling operation of the engine, and this in turn increases the amount of harmful components included in the exhaust gas. Furthermore, such non-uniform output gives rise to engine vibration which in turn causes noise and other disadvantages.
In order to overcome the above problems, there have been proposed various apparatuses for controlling the fuel injected into the respective cylinders of the internal combustion engine according to an individual cylinder control method. Japanese Patent Application Public Disclosure No. 82534/84 discloses an example of an apparatus of this type in which individual cylinder control is carried out on the basis of the result of a detection carried out for every combustion stroke in each cylinder, of the difference between the rotational speed at the time of the combustion of fuel supplied by injection to the multi-cylinder internal combustion engine and the rotational speed at the time when the instantaneous rotational speed of the crankshaft reaches maximum value as a result of the above-mentioned combustion.
However, the conventional apparatuses of this type directly use the result of the individual cylinder control calculation as data for determining the target injection amount in idling operation control, making the response characteristics of the control system a problem in the case where the number of cylinders of the engine is great. The conventional apparatuses thus have the disadvantage that the individual cylinder control operation is hindered. More specifically, when the target idling speed is high or the number of cylinders is numerous, the time period from calculation and output of the target value of the amount of fuel injection for each cylinder to the actual fuel injection into that cylinder is shortened to such an extent that there is insufficient time for the servosystem to perform the operation for regulating the actual injection amount in response to the determination of the target value.
In order to overcome this disadvantage, it is effective to employ a method which lowers the frequency of the drive pulse signal of the governor system so as to increase the frequency response of the governor system. However, this method gives rise to other problems, e.g., a change in the output torque of the engine is caused even by a small vibration of the governor and the method can be implemented only by the use of bulky equipment.